Three-Point Method

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‌Three-Point Method ‌

Here’s the simplest and most widely applicable way to set up a coordinate system. It is strongly recommended unless there is a compelling reason for an

alternative. SynthEyes has a special button to help make it easy. We’ll describe how to use it, and what it is doing, so that you might understand it, and be able to modify its settings as needed.

Switch to the Coordinate System control panel. Click the *3 button; it will now read Or. Pick one tracker to be the coordinate system origin (ie at X=0, Y=0, Z=0).

Select it in the camera view, 3-D viewport, or perspective window. On the coordinate system panel, it will automatically be changed from Unconstrained to Origin. Again, any tracker can be made the origin, but some will make more sense and be more convenient than others.

Important : Zero-weighted trackers must not be used to set up a coordinate system, or as part of distance constraints. Constraints on ZWTs are permitted, but affect only that ZWT.

The *3 button will now read LR (for left/right). Pick a second tracker to fall along the X axis, and select it. It will automatically be changed from Unconstrained to Lock Point; after the solution it will have the X/Y/Z coordinates listed in the three spinners.

Decide how far you want it to be from the origin tracker, depending on how big you want the final scene to be. Again, this size is arbitrary as far as SynthEyes is concerned. If you have a measurement from the set, and want a physically-accurate scene, this might be the place to use the measurement. One way or another, decide on the X axis position. You can guess if you want, or you can use the default value, 20% of the world size from the Solver panel. Enter the chosen X-axis coordinate into the X coordinate field on the control panel.

The *3 button now reads Pl. Pick a third point that should be on the ground plane. Again, it could be any other tracker―except one on the line between the origin and the X-axis tracker. Select the tracker, and it will be changed from Unconstrained to On XY Plane (if you are using a Z-Up coordinate system, or On XZ Plane for Y-up coordinates). This completes the coordinate system setup, so the *3 button will turn off.

The sequence above places the second point along the X axis, running from left to right in the scene. If you wish to use two trackers aligned stage front to stage back, you can click the button from LR (left/right) to FB (front/back) before clicking the second tracker. In this case, you will adjust the Y or Z coordinate value, depending on the coordinate system setting.

You might wonder which trackers get selected to be constrained: Tracker37 or Tracker39, etc. You should pick the trackers that create the coordinate system that you want to see in the animation/compositing package, the coordinate system that makes your later work easier.

To provide the most accurate alignment, you should select trackers spread out across the scene, not lumped in a particular corner. You should also use trackers with low error (from the Tracker or Coordinate System panels) that are comparatively long- lived through the shot.

Depending on your desired coordinate system, you might select other axis and plane settings. You can align to a back wall, for example. For the more complex setups, you will adjust the settings manually, instead of using *3.

You can lock multiple trackers to the floor or a wall, say if there are tracking marks on a green-screen wall. This is especially helpful in long traveling shots. If you are tracking objects on the floor, track the point where the object meets the floor; otherwise you’ll be tracking objects at different heights from the floor (more on this in a little). If you add additional constraints, you should be sure to verify that they are OK (configured right, and match the real world) using the Constrained Points View.

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